Generally, wireless communication uses a limited frequency resource. Therefore, wireless signals that are different from or identical to each other are transmitted and received within a narrow band. Consequently, interference occurs between frequencies. The interference occurring between frequencies may be classified roughly into co-channel interference and adjacent channel interference according to the type of interference. According to the to the related art, various techniques for canceling co-channel interference and adjacent channel interference are used depending on the employed technology of wireless communication. When interference cancellation techniques are indiscreetly used even in a case in which no interference is present, performance may be degraded. Therefore, techniques for detecting whether there is interference are already known.
For example, means for detecting whether interference occurs and for canceling interference according to a result of detection may be configured as illustrated in FIG. 1.
FIG. 1 is a diagram illustrating a block configuration of a unit for detecting and canceling interference in a wireless communication system according to the related art.
Referring to FIG. 1, the interference cancellation means includes an interference detection and control unit 110 and an interference cancellation unit 120. The interference detection and control unit 110 detects an interference signal and controls application of interference cancellation techniques depending on a situation. The interference cancellation unit 120 cancels interference from a received signal according to the control of interference detection and control unit 110. The interference detection and control unit 110 detects the magnitude of the interference signal and controls the interference cancellation unit 120 according to the magnitude. The interference detection and control unit 110 and the interference cancellation unit 120 use different signal processing methods according to the types of the interference signal (e.g., adjacent channel interference signal and co-channel interference signal).
Interference cancellation techniques according to the related art consider only one type interference. Therefore, when two or more multi-interferences are cancelled, high operation complexity is required. Generally, in an area in which frequency resources are scarce, a multi-interference having two types of interferences occurs in many cases. Therefore, in a receiving apparatus having a plurality of interference cancellation devices, interference is cancelled by applying respective interference cancellation devices according to a situation. In this case, when two or more interference cancellation units are used, and the respective interference cancellation devices are influenced by one another, the receiving apparatus is required to determine the influence of the respective interference cancellation devices in advance and to control the respective cancellation units. However, in practice, determining the effects that the respective cancellation units have on one another in advance is very difficult or nearly impossible.
A receiving system for canceling a multi-interference signal using a plurality of cancellers for canceling a single type interference signal in a wireless communication system is configured as illustrated in FIG. 2. An interference signal generally needs to be cancelled before an equalization unit. Therefore, when two or more interference cancellation units are used, the interference cancellers are connected in series as illustrated in FIG. 2.
FIG. 2 is a diagram illustrating a block configuration of a receiving apparatus including a plurality of interference cancellation units in a wireless communication system according to the related art.
Referring to FIG. 2, a first interference detection and control unit 210-1 and a first interference cancellation unit 220-1 are provided in order to cancel first interference, and a second interference detection and control unit 210-2 and a second interference cancellation unit 220-2 are provided in order to cancel second interference. In this case, the blocks for canceling the first interference (e.g., the first interference detection and control unit 210-1 and the first interference cancellation unit 220-1) and the blocks for canceling the second interference (e.g., the second interference detection and control unit 210-2 and the second interference cancellation unit 220-2) are connected in series. A channel estimation unit 230, an equalization unit 240, and a channel decoder 250 are connected subsequently thereto.
A problem does not occur when a plurality of interference cancellation units operate independently without interfering with each other. However, the signal processing algorithms of employed interference cancellation units influence each other with respect to signal processing methods as a result of the characteristics thereof. In addition, when reception performance is influenced due to the above-described reason, the respective interference cancellation units connected in series as illustrated in FIG. 2 may not be controlled independently. For example, when co-channel interference and adjacent channel interference both exist, the case of using only a co-channel interference cancellation unit may represent better performance than the case of using both the co-channel interference cancellation unit and an adjacent channel interference cancellation unit. The reason for this is that the characteristics of the adjacent channel interference cancellation unit has an influence on the signal processing process of the co-channel interference cancellation unit, so that the quality of a received signal is degraded in a co-channel interference cancellation process.
As described above, when two types of interference signals exist, the receiving apparatus needs to estimate influence occurring between interference cancellation units and determine an optimal control combination. However, determining the influence between interference cancellation units is difficult, thereby hardly determining the optimal control combination.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.